According to the state demographer for Texas (Eschbach & Fonseca, 2009), childhood obesity has more than doubled in the past 20 years, and overweight/obesity rates for Texas fourth graders are twice the national average for fourth grade students. In addition, obesity rates for Latino and African American children in Texas are among the highest in the nation. This is problematic because 70 percent of overweight and obese youth become overweight and obese adults, which significantly increases the risk other chronic diseases. In Brazos County, Texas, a group of local stakeholders have identified and prioritized childhood obesity as a key community issue. These stakeholders have been loosely networked, and the current project will strengthen that network to build on resources and capacities to engage in policy-relevant research. Most school-based childhood obesity interventions target some aspect of energy balance-either reducing the calories consumed or increasing physical activity. The gap in those programs has been affecting physical activity during the entire school day. Dynamic classrooms-using stand-biased workstations for students-are a relatively low-cost, low-effort method of passively increasing children's physical activity during instructional time, as standing burns up to 30 percent more calories than sitting in children at this age. The stand/sit desks allow students to stand or sit at their discretion, without being disruptive or conspicuous among their classmates. The dynamic classroom study seeks to achieve four specific aims: AIM 1: To strengthen support of community stakeholders for policy-relevant childhood obesity research in Brazos County. AIM 2: To measure the degree to which stand-biased workstations increase calorie expenditure and reduce body fat percentage (impedance method) and body mass index in first and second grade students over the course of two academic years. AIM 3: To investigate whether stand/sit workstations improve students' classroom performance, specifically behavioral engagement and academic achievement. AIM 4: To identify factors that promote or inhibit the implementation and use of the stand/sit desks in classroom settings. The study seeks to examine health and academic outcomes in order to present comprehensive information to schools that has the potential to impact policy at the school, district, state, and national levels. Relevant to NICHD's mission, this intervention has the potential to reach the vast majority of children through the public school system, enhancing their ability to stay healthy and be successful in their education and increasing their chances of a full and productive life.